The degradation of xenobiotic branched carboxylic acids in anaerobic sediment of the Pearl River in Southern China

Xenobiotic branched carboxylic acids (BCAs) discharged by industries are of ten persistent in biological wastewater treatment systems and end up in wat er and sediments. In this study, the degradation of 12 typical BCAs in an a naerobic environment of river sediment was studied in vitro using enrichmen t shake-flask cultures. The anaerobic consortium taken from the river sedim ent, comprising BCA-degrading and methane-producing genera, degraded BCAs w ith tertiary carbons through beta-oxidation, followed by methanogenesis mec hanisms. The maximum cell densities in the cultures using BCAs as the sole carbon source ranged between 5.0 and 6.0 x 10(5) cells/ml. The maximum degr adation rates were between 5.0 and 8.5 x 10(-3) mmol/h. The consortium coul d not degrade BCAs with quaternary carbons. The degree of branching at the alpha or beta position along the carbon chain interfered with the beta-oxid ation mechanisms. These BCAs would accumulate in the sediment and significa ntly affect the cycling of organic carbon and nutrients. (C) 2001 Elsevier Science B.V. AU rights reserved.